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https://github.com/propensive/hyperbole

Assintance with Scala 3 metaprogramming
https://github.com/propensive/hyperbole

compile-time macros metaprogramming scala static-analysis

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Assintance with Scala 3 metaprogramming

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README 

        
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# Hyperbole



__Assistance with Scala 3 metaprogramming__



Hyperbole is a nascent set of tools to make it easier to write macros in Scala.

To begin, it includes an `introspect` method which can provide useful

reflection detail about how the source of an expression translates into an AST.



## Features



- See a full introspection of an expression's AST

- Renders the AST structure in an easy-to-read tree format

- View source code alongside the AST

- Also view the "expanded" source code alongside, showing "invisible" syntax

- Produces output at compiletime or runtime, invoked inside or outside of a macro



## Availability Plan



Hyperbole has not yet been published. The medium-term plan is to build Hyperbole

with [Fury](https://github.com/propensive/fury) and to publish it as a source build on

[Vent](https://github.com/propensive/vent). This will enable ordinary users to write and build

software which depends on Hyperbole.



Subsequently, Hyperbole will also be made available as a binary in the Maven

Central repository. This will enable users of other build tools to use it.



For the overeager, curious and impatient, see [building](#building).



## Getting Started



Hyperbole runs at compiletime to inspect an expression, but can present its

output in different ways:

- as a message reported at compiletime

- as a terminal compile error

- as a value which can be used in some way at runtime



It can be invoked on an expression in ordinary code, or in an inline context

where a `Quotes` instance is available, on a lifted `Expr` or a `Tree` value.



In all cases, the macro is invoked with an `introspect` method, either passing

the expression to be inspected, or a lifted `Expr` expression value in a quoted

context, disambiguated by overloading. In a quoted context, an additional

optional parameter, `terminate`, may be specified as `true` to indicate that

the output should be reported as a compiler error rather than an informational

message at compiletime; by default it is `false`.



A contextual `Introspection` value determines what result should be yielded

from a call to `introspect`. This given value can determine not only the result

type, but whether the expression is evaluated or its value retained. Three

implementations offered:



- `introspection.println`—records the introspection details to `stdout` with

  `println`, and returns the expression value

- `introspection.text`—constructs a `Text` value containing the introspection

  details, ignoring the expression without evaluating it



The default is to log using Eucalyptus. Note that this contextual value is not

necessary for the `introspect` method that take an `Expr` value.



For example, in a macro method body,

```scala

import hyperbole.*

def macroImpl(expr: Expr[T])(using Quotes): Expr[Unit] =

  import quotes.reflect.*

  introspect(expr, terminate = true)

```

or, for example, in a [Probably](https://github.com/propensive/probably/) test,

```scala

import hyperbole.*, introspection.log

import probably.*

import eucalyptus.*, logging.stdout



test(t"Two joined lists are not empty"):

  val xs = List(1)

  val ys = List(2)

  introspect(xs ++ ys)

.assert(!_.isEmpty)



```



## Status



Hyperbole is classified as __embryonic__. For reference, Scala One projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Hyperbole is designed to be _small_. Its entire source code currently consists

of 79 lines of code.



## Building



Hyperbole will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Hyperbole?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Hyperbole's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Hyperbole and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `hyperbole`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Hyperbole's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Hyperbole are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/hyperbole/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Hyperbole

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Hyperbole was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



_Hyperbole_ is a tool for working with macros (short for _macroinstructions_) whose name implies a large—or hyperbolic—size.



In general, Scala One project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows a set of shapes formed from hyperbolic curves, reminiscent of a butterfly.



## License



Hyperbole is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).